Vlodavsky I, Elkin M, Pappo O, Aingorn H, Atzmon R, Ishai-Michaeli R, Aviv A, Pecker I, Friedmann Y
Department of Oncology, Hadassah-Hebrew University Hospital, Jerusalem, Israel.
Isr Med Assoc J. 2000 Jul;2 Suppl:37-45.
Expression of heparan sulfate-degrading endoglycosidases, commonly referred to as heparanases, correlates with the metastatic potential of tumor cell lines, and treatment with heparanase inhibitors markedly reduces the incidence of metastasis in experimental animals. We purified a 50 kDa heparanase from human hepatoma and placenta and cloned a cDNA and gene encoding a protein of 543 amino acids. Only one heparanase sequence was identified, suggesting that this enzyme is the dominant endoglucuronidase in mammalian tissues. Expression of the cloned cDNA in insect and mammalian cells yielded 65 kDa and 50 kDa recombinant proteins. The 50 kDa enzyme represents an N-terminal processed enzyme that is at least 200-fold more active than the full-length 65 kDa form. Processing was demonstrated following incubation of the full-length recombinant enzyme with intact tumor cells. The heparanase mRNA and protein are preferentially expressed in metastatic cell lines and in specimens of human melanomas and carcinomas. In the colon, both the heparanase mRNA and protein are expressed already at the stage of tubulovillous adenoma, but not in the adjacent 'normal-looking' colon epithelium. Non-metastatic murine T lymphoma and melanoma cells transfected with the heparanase gene acquired a highly metastatic phenotype in vivo. Apart from its involvement in the egress of cells from the vasculature, heparanase is tightly involved in angiogenesis, both directly--by promoting invasion of endothelial cells (vascular sprouting), and indirectly--by releasing heparan sulfate-bound basic fibroblast growth factor, and generating HS degradation fragments that promote bFGF activity. The angiogenic potential of heparanase was demonstrated in vivo (Matrigel plug assay) by showing a three to fourfold increase in neovascularization induced by Eb T lymphoma cells following their transfection with the heparanase gene. The ability of heparanase to promote both tumor angiogenesis and metastasis makes it a promising target for cancer therapy.
硫酸乙酰肝素降解内切糖苷酶（通常称为乙酰肝素酶）的表达与肿瘤细胞系的转移潜能相关，用乙酰肝素酶抑制剂治疗可显著降低实验动物的转移发生率。我们从人肝癌组织和胎盘中纯化出一种50 kDa的乙酰肝素酶，并克隆了编码一个543个氨基酸蛋白质的cDNA和基因。仅鉴定出一个乙酰肝素酶序列，这表明该酶是哺乳动物组织中主要的内切葡糖醛酸酶。在昆虫和哺乳动物细胞中表达克隆的cDNA可产生65 kDa和50 kDa的重组蛋白。50 kDa的酶是一种N端加工后的酶，其活性比全长65 kDa形式至少高200倍。将全长重组酶与完整肿瘤细胞孵育后证实了这种加工过程。乙酰肝素酶mRNA和蛋白在转移细胞系以及人类黑色素瘤和癌组织标本中优先表达。在结肠中，乙酰肝素酶mRNA和蛋白在管状绒毛状腺瘤阶段就已表达，但在相邻的“外观正常”结肠上皮中不表达。用乙酰肝素酶基因转染的非转移性小鼠T淋巴瘤和黑色素瘤细胞在体内获得了高度转移表型。除了参与细胞从脉管系统逸出外，乙酰肝素酶还紧密参与血管生成，直接促进内皮细胞侵袭（血管芽生），间接通过释放硫酸乙酰肝素结合的碱性成纤维细胞生长因子以及产生促进bFGF活性的HS降解片段来实现。通过显示用乙酰肝素酶基因转染的Eb T淋巴瘤细胞诱导的新生血管形成增加三到四倍，在体内（基质胶植入试验）证明了乙酰肝素酶的血管生成潜能。乙酰肝素酶促进肿瘤血管生成和转移的能力使其成为癌症治疗的一个有前景的靶点。
